Association between acute exacerbation and progressive pulmonary fibrosis in interstitial lung disease: a retrospective cohort study.

Background: Acute exacerbation (AE) refers to rapidly progressive respiratory deterioration in the clinical course of interstitial lung disease (ILD). Progressive pulmonary fibrosis (PPF) is the chronic progressive phenotype of ILD. No study has investigated the relationship between AE and PPF in ILD.

Objectives: We aimed to determine the association between AE and PPF in ILD patients.

Design: A retrospective cohort study.

Methods: A total of 414 patients hospitalised for ILD were included in our study. The clinical presentations, radiographic features and laboratory findings of the patients were reviewed.

Results: AE was present in 120 (29.0%) ILD patients and was associated with a higher risk of death than non-AE patients in the whole cohort (HR 2.893; 95% CI, 1.847-4.529; p < 0.001). However, the significant difference disappeared when stratified by PPF (HR 1.192; 95% CI, 0.633-2.247; p = 0.586) and non-PPF (HR 1.113; 95% CI, 0.384-3.223; p = 0.844). In addition, the adverse effect of PPF on prognosis remained consistent in both AE and non-AE patients. Multivariable logistic regression analysis showed that compared with non-PPF patients, only age was a risk factor for PPF in AE-ILD, while the risk factors for PPF in the non-AE group were age, definite usual interstitial pneumonia and mediastinal lymph node enlargement.

Conclusion: In the context of ILD, both AE and PPF were found to be associated with poor prognosis. However, the adverse effect of AE on prognosis disappeared when PPF was considered as a stratification feature, whereas the adverse effect of PPF on prognosis persisted in both AE and non-AE individuals. Therefore, it is important to investigate effective strategies to prevent disease progression after AE. Increased recognition and attention to PPF and early antifibrotic therapy at the appropriate time is also warranted.